i'm trying to test a new 9P fs with 9pcon. after posting the file server's
fd to /srv, it can be mounted (e.g. mount /srv/foo /n/foo) and walked
correctly.  trying 9pcon on the same fd (e.g. aux/9pcon /srv/foo) results
in "inappropriate use of fd".

any ideas?  fyi, the 9p code is from scartch based on re-re-reading of
0intro(5) docs, so it is entirely possible i missed something subtle that
9pcon doesn't tolerate.